US regulators have accused a Dutch trading business and three senior employees including its British head trader of manipulating energy futures contracts on the New York Mercantile Exchange (Nymex.)

The US Commodity Futures Trading Commission (CFTC) alleges that Optiver Holding and its staff attempted to manipulate markets in gasoline futures relating to the light sweet crude oil and other energy commodities during March 2007.

Christopher Dowson, a British citizen named in the lawsuit as Optiver's head of trading , is accused of taking part in the alleged manipulation.

The CFTC says the firm tried to manipulate prices 19 times and succeeded in causing artificial prices on five occasions, earning about $1 million (£500,000) in profit, according to a lawsuit filed in US District Court in New York.

Optiver did not return calls seeking comment.

The lawsuit comes just days after the US Congress began deliberating legislation that would require the CFTC to set limits on trading in oil markets by investors and speculators.

It would also close a loophole that allows speculators trading on the London oil market to escape scrutiny by U.S. regulators.

Stephen Jay Obie, the CFTC’s acting director of enforcement, said the investigation had been under preparation for some time.

“This is not a politically motivated case,” he said. “What we are going after are manipulators of our marketplace.”

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